It is often important to determine properties such as the resistance of a soil to liquefaction, the degradation characteristics of a soil, the dynamic shear modulus of a soil at low levels of shear deformation, and the variation in the shear modulus of a soil with shear deformation. Commonly, these soil properties, as well as others, are necessary for the analysis which predicts the response of a site or foundation structure system to dynamic loading caused by earthquakes, ocean waves, or mechanical vibrations.
Soil properties may be determined by in situ field tests. For example, the liquefaction resistance of a soil may be determined by a penetration test that involves penetrating a closed ended probe into the ground at a slow, controlled rate or driving a cylinder into the ground by violent impacts. The resistance of the soil to liquefaction is correlated to the resistance of the probe or cylinder to penetration. A technique that can measure the resistance of a soil to liquefaction by torsionally exciting the soil is disclosed in the U.S. Pat. Nos. 4,594,899 and 5,203,824 to Robert Henke and Wanda Henke. In these patents, the illustrated testing device includes a pair of concentric open ended cylinders that are inserted into the soil to be tested. A torque may be applied to the inner cylinder and the response of the cylinder and the soil to the applied torque may be measured by sensors mounted on the inner cylinder.
In such soil tests a borehole is drilled to access the soil sample and the testing device is lowered down the borehole to test the soil. The testing device may be secured to an auger in the borehole. The test device may be subjected to substantial applied forces or torques or other reaction forces from the soil. Thus the auger to which the testing device is anchored may serve as a reaction means to carry out various operations on the testing device.
If the testing device is not properly secured to the auger, the testing device may slip from the auger as a result of the reaction forces produced by the applied forces or torques on the testing device. There is a need for a device that better secures the testing device to the auger.
The testing device should maintain a correct orientation with respect to the soil sample, even when the testing device is subjected to applied forces or torques. This is because improper orientation of the testing device may cause inaccuracies in test results or damage to the testing device.